The 0/4 he makes when he enters can protect Teyo and your other planeswalkers, and his -2 can allow you to make it so only one player will be able to attack you or your walkers over the next turn cycle
and, of course, Lier, Disciple of the Drowned
Some cards allow you to behold a dragon to get additional benefits, like Sarkhan, Dragon Ascendant, Dispelling Exhale, or even Celestial Reunion if you choose dragons
Demolisher Spawn Demolisher Spawn is comparable to End-Raze Forerunners if deliriums online, which isnt very hard at the point in the game where youre casting a 7-drop
Maybe the defensive potential of steel
Thankfully, there really isnt a particular dud among these precons so you cant go too far wrong no matter which one you land on buying